A data center is required to handle large amounts of data while securing reliability, so that a redundant array of inexpensive disks (RAID) scheme using a plurality of hard disk drives (HDDs) is generally employed.
Therefore, an HDD diagnoses a write head or a recording medium (disk) in order to secure the reliability of the HDD. For example, in the HDD, a write patrol is performed, in which a predetermined area of a disk is set as a diagnosis area and an operation of the write head is confirmed by writing an inspection data into the diagnosis area or reading the written inspection data from the diagnosis area.
Related techniques are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2001-35096, Japanese Laid-Open Patent Publication No. 2003-228925, and International Publication Pamphlet No. WO 2009/040929.
As a storage capacity of an HDD (a storage apparatus) is further increased, the diagnosis area becomes relatively smaller compared to a user area and thus the head may reside in a fixed point floating state. Even though the HDD may avoid the fixed point floating state of the head by expanding the diagnosis area, the expansion may cause another problem that an area which may not be used as the user area is increased.
Further, when a timing of input/output (I/O) request and a timing of diagnosis are coincident with each other, the diagnosis operation of the HDD affects the I/O performance.